1. Field of the Invention
The present invention relates to an image forming apparatus, an image forming system, and an image forming method for correcting a deviation of position to which an image is transferred caused by meandering of a recording medium such as a sheet.
2. Description of the Related Art
In an image forming apparatus, a charged photosensitive member is exposed on the basis of image data to form an electrostatic latent image, and a developer (toner) is made to adhere to the photosensitive member to develop the electrostatic latent image into a toner image. The toner image is then transferred to a recording medium such as a sheet (hereinafter referred to as a sheet), and the sheet onto which the toner image is transferred is heated and pressure is applied thereto by a fixing roller to fix the toner image on the sheet.
In such an image forming apparatus, if a sheet is deviated and passes a transfer position in a state in which the sheet is deviated to one side from a reference position, a problem that the position of the image transferred onto the sheet is deviated is caused. Furthermore, when a long sheet that is conveyed for transfer in a state in which the sheet is held between pre-transfer rollers, by a secondary transfer part and between fixing rollers at the same time is used, the sheet is likely to meander owing to the difference in the roller diameter.
In this regard, a technology for detecting a deviation of a sheet being conveyed to correct the position to which an image is to be written is proposed (refer to JP 8-230231 A). In the image forming apparatus disclosed in JP 8-230231 A, detection of the position of an end of a sheet is also performed while the sheet is being conveyed so that the write position is always corrected when a deviation occurs.
For detecting a deviation of a sheet being conveyed and correcting a position to which an image is to be written, the angle of the image (vertical magnification and horizontal magnification) needs to be changed according to the meandering angle of the sheet when the meandering sheet passes through a transfer position at an angle from a reference position. Thus, write control of images is complicated and correction of an image with respect to the sheet is difficult. As a result, the accuracy of the image position with respect to the sheet is not stable.